The invention concerns an electronic arrangement, namely, a special reference source, which yields a reference voltage, or a reference current of defined magnitude. The invention was developed in particular in n-channel technology for the feeding of the R/2R-networks of D/A converters, that is, PCM/AM decoders, and above all, of A/D converters, that is, AM/PCM coders, in particular also for charge-to-voltage, as well as for voltage-to-charge converters of CCD filters of a special PCM telephone exchange system which is constructed out of highly integrated modules. In such an application, the reference sources, R/2R-networks, other converter elements and also the filter are located on the same FET module. The invention is suited however, above and beyond this for various FET modules, which require a substantially exactly adjustable reference voltage, or a subsequently very exactly adjustable reference current.
The invention proceeds from a reference source on an integrated FED module, whereby
two separated levels which are however supplied by the same direct current source, in each case contain series circuiting of at least a IG-FET and at least one load resistor, PA1 in each case a tap is applied between one of the IG-FETs and one of the load resistors in each stage, and PA1 between the taps of the stages, a difference voltage of defined value appears, which is used directly as a reference voltage, or which indirectly is used for the adjustment of the value of a reference voltage, or respectively, of a reference current, for example, by means of a bleeder. PA1 two separated stages, which, however, are fed by the same direct current supply source, in each case contain the series circuiting of at least one IG-FET and at least one load resistor; PA1 in each case, a tap is applied between one of the IG-FETs and one of the load resistors in each stage; and PA1 between the taps of the stages, a differential voltage of defined value occurs, which is used directly itself as the reference voltage, or which is used indirectly for the setting of the value of a reference voltage, or respectively, of a reference current, for example, by means of a voltage divider.
Such a reference source is already specified in ESSCIRC (European Solid State Circuitry Conference) 1977, Ulm. Sept. 20-22, 1977, Digest of invited papers and contribution papers, pages 43 through 47, in particular page 44, right column, second to last paragraph. It is also encouraged to construct the IG-FETs of both stages differently, namely, on the one side with a depletion type channel area, on the other side with an enhancement type channel area, in order to utilize their different threshold voltages. There, however, finally also the necessity is pointed out that first development efforts are still necessary before a reference source for an integrated module is found which is also usable. The divergences of characteristics because of the unavoidable tolerances in the case of the production are in this case apparently very inconvenient. In particular, the applying of different channel area types in the two stages has as a result inconveniently difficult problems with respect to the tolerances which are bound up with this.